Metallurgical plant with efficient waste-heat utilization

ABSTRACT

A metallurgical plant has a plant positioned upstream of a steel-generating plant and has a gas-generating plant which generates an export gas. Carbon dioxide and/or water contained in the export gas is removed from the export gas in a separation device. A resulting product gas is heated, before being supplied to the upstream plant, in a firing unit through the combustion of a heating gas. Excess thermal energy produced during the combustion of the heating gas which is not used for heating the product gas is thermally utilized. The utilization may take place within the firing unit through steam generation and/or downstream of the firing unit to preheat the heating gas and/or an oxidation gas used for the combustion of the heating gas and/or through the pre-heating and/or drying of raw materials to be supplied to the upstream plant and/or to the gas-generating plant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to International Application No. PCT/EP2012/053975 filed on Mar. 8, 2012 and Austrian Application No. A368/2011 filed on Mar. 17, 2011, the contents of which are hereby incorporated by reference.

BACKGROUND

The present invention relates to an operating method for a metallurgical plant that has a plant disposed upstream of a steelmaking plant in the production process for steel and a gas-generating plant which generates an export gas,

-   -   wherein carbon dioxide and/or water contained in the export gas         are/is at least partially removed from the export gas in a         separation device and a product gas resulting thereby is heated         in a firing device through combustion of a heating gas before         being supplied to the upstream plant,     -   wherein the heating gas is supplied to the firing device in         quantities significantly greater than are required for heating         the product gas.

The present invention further relates to a metallurgical plant.

Metallurgical plants and the associated operating methods are known from U.S. Pat. No. 5,846,268 A.

In metallurgical plants, in particular in plants in the iron- and steelmaking industry, there is a requirement for large amounts of thermal energy at high temperatures. Large amounts of waste heat therefore accumulate in plants of said kind. Part of the waste heat being generated is already utilized for preheating intermediate products—in particular process gases—accumulating or to be processed inside the metallurgical plant. Part of the waste heat is also utilized already for driving an electric generator in addition to a downstream turbine by way of a steam-generating device.

SUMMARY

One potential object relates to providing possibilities for more efficient utilization of a metallurgical plant of the type cited in the introduction.

The inventors propose an operating method for a metallurgical plant of the type cited in the introduction in such a way

-   -   that the thermal energy produced during the combustion of the         heating gas, insofar as it is not used for heating the product         gas, is thermally utilized within the firing device for steam         generation and/or in relation to the gas flow of the flue gas         resulting from the combustion of the heating gas downstream of         the firing device for preheating and/or drying raw materials         that are to be supplied to the upstream plant and/or to the         gas-generating plant.

In a preferred embodiment the flue gas resulting during the combustion of the heating gas is used for steam generation in the first instance, and only thereafter for heating the product gas.

In certain cases it is necessary to keep the temperature of the product gas substantially constant at a setpoint temperature. If this is the case and the temperature of the flue gas is too high, it is possible to add cold-blast air to the flue gas after its use for steam generation and before the product gas is heated in order to adjust the temperature of the flue gas heating the product gas.

In a particularly preferred embodiment it is provided

-   -   that the heating of the product gas is limited to an         intermediate temperature below a reaction temperature required         for the use of the product gas in the upstream plant, although         the thermal energy necessary for this is generated during the         combustion of the heating gas, and     -   that the heated product gas is heated up from the intermediate         temperature to the reaction temperature by a partial oxidation         of the product gas.

If the thermal energy of the flue gas is sufficiently great, it is possible to use the thermal energy of the flue gas downstream of the firing device for preheating the heating gas and/or for preheating an oxidation gas used for incinerating the heating gas and/or for heating a thermal oil.

It is possible to use some of the export gas generated by the gas-generating plant as heating gas. Alternatively or in addition it is possible to use a process gas produced during the removal of the carbon dioxide and the water from the export gas and enriched with carbon dioxide and water as heating gas. If the said process gas does not burn with sufficient stability or does not contain the necessary thermal energy, a further combustible gas can be mixed with the process gas or the process gas can be incinerated in conjunction with the further combustible gas.

The amount and/or the composition of the accumulating export gas and, associated therewith, also the amount and/or the composition of the accumulating process gas are often subject to severe fluctuations with time. In many cases it can therefore be beneficial to buffer the fraction of the export gas used as heating gas or the process gas in a low-pressure gas accumulator disposed upstream of the firing device.

In many cases a combustible gas is generated during the operation of the upstream plant. It is possible for at least some of the combustible gas to be mixed with the export gas. Alternatively or in addition the combustible gas can be used as heating gas. In particular the last-cited combustible gas can be added where appropriate to the aforementioned process gas enriched with carbon dioxide and water, or incinerated together with said process gas.

It is furthermore possible for a hot top gas to accumulate during the operation of the upstream plant. In this case it is possible for the thermal energy contained in the top gas to be used for preheating the product gas before the latter is supplied to the firing device and/or for steam generation. Alternatively the hot top gas can be a combustible or a noncombustible gas.

The upstream plant can be embodied for example as a blast furnace, as a smelting reduction plant, as a smelter unit or as a direct reduction plant. The gas-generating plant can be embodied for example as a coal gasification plant or as a metal smelting plant, in particular as an iron melting plant or as a smelting reduction plant.

The inventors also propose a metallurgical plant that performs the proposed operating method.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram representing a metallurgical plant,

FIG. 2 is a schematic diagram representing a detail of the metallurgical plant from FIG. 1, and

FIG. 3 is a schematic diagram representing a possible embodiment of the metallurgical plant from FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

According to FIG. 1, a metallurgical plant has a gas-generating plant 1. The gas-generating plant 1 can be embodied for example as a coal gasification plant or as a metal smelting plant. In the case of an embodiment as a metal smelting plant this can be embodied in particular as an iron melting plant—also as a blast furnace, in particular an oxygen blast furnace—or as a smelting reduction plant. An oxygen blast furnace is a blast furnace in which technically pure oxygen is used as hot-blast air and the resulting stack gas can be returned to the blast furnace.

During operation the gas-generating plant 1 generates a gas 2, referred to hereinbelow as export gas 2. The export gas 2 contains combustible components as well as, in addition, carbon dioxide, water and typically also nitrogen. The presence of carbon dioxide and water is indicated in FIG. 1 by the suffixes “CO₂” and “H₂O” appended to the export gas.

All or part of the export gas 2 is supplied to a separation device 3. The export gas 2—possibly only the fraction of the export gas 2 supplied to the separation device 3—is conditioned in the separation device 3. In particular the carbon dioxide contained in the export gas 2 and/or the water contained in the export gas 2 are/is completely or partially removed from the export gas 2 in the separation device 3. This results on the one hand in a product gas 4 in which carbon dioxide and water are depleted in comparison with the export gas 2. This is indicated in FIG. 1 by the suffixes “CO₂—” and “H₂O—”. On the other hand a process gas 5—often referred to as tail gas—is produced in which carbon dioxide and/or water are enriched. This is indicated in FIG. 1 by the suffixes “CO₂+” and “H₂O+”.

The product gas 4 is initially supplied to a firing device 6 and from there to an upstream plant 7. The upstream plant 7 is a plant which is disposed upstream of a steelmaking plant 8 in the steel production process. The upstream plant 7 can be embodied for example as a blast furnace, as a smelting reduction plant, as a smelter unit or as a direct reduction plant.

In the firing device 6, the product gas 4 is heated in a product gas heat exchanger 9. In the process the chemical composition of the product gas 4 remains—at least substantially—unchanged. Only the temperature of the product gas 4 changes.

When the firing device 6 is fired, a heating gas 11 is incinerated into a flue gas 12 in the firing device 6 using an oxidation gas 10. Both gases 10, 11 are supplied to the firing device 6. The oxidation gas 10 can in particular be normal air.

The heating gas 11 is supplied to the firing device 6 in quantities significantly greater than are required for heating the product gas 4. For this reason a substantial amount of surplus thermal energy accumulates in the firing device 6. Insofar as it is superfluous, i.e. is not needed and utilized for heating the product gas 4, the resulting thermal energy can be used for example for generating steam inside the firing device 6 by an evaporator 13 and thus for driving a water-steam circuit. For example, the steam can drive a turbine 14 which in turn drives an electric generator 15. Alternatively, the steam can be utilized for other purposes.

If steam is generated, the evaporator 13—seen particularly clearly in FIG. 2—is positioned upstream of the product gas heat exchanger 9 in relation to the gas flow of the flue gas 12. The flue gas 12 resulting from the combustion of the heating gas 11 is therefore utilized for steam generation in the first instance, and only thereafter for heating the product gas 4.

Where necessary, the generated steam can also be superheated by the flue gas 12. If present, a superheater (not shown in the FIGs) is in this case positioned upstream of the product gas heat exchanger 9, and possibly also the evaporator 13, in relation to the gas flow of the flue gas 12. In addition, the water that is to be vaporized can be preheated. A corresponding preheater (not shown in the FIGs) is in this case disposed downstream of the product gas heat exchanger 9 in relation to the gas flow of the flue gas 12.

Alternatively or in addition to its being utilized for steam generation it is possible for the flue gas 12 to be used in units 16 to 19 which are disposed downstream of the firing device 6 in relation to the gas flow of the flue gas 12.

For example, the heating gas 11 can be preheated in a heating gas heat exchanger 16. Alternatively or in addition to the preheating of the heating gas 11, the oxidation gas 10 can be preheated in an oxidation gas heat exchanger 17. The preheating of the heating gas 11 and/or of the oxidation gas 10 clearly takes place before the said gases 10, 11 are supplied to the firing device 6.

Furthermore—alternatively or in addition to the preheating of the heating gas 11 and/or of the oxidation gas 10—raw materials 20 that are to be supplied to the upstream plant 7 can be dried and/or preheated in a raw materials processing device 18. Analogously, in addition or alternatively, raw materials 21 that are to be supplied to the gas-generating plant 1 can be dried and/or preheated in a further raw materials processing device 19. Iron ore or metallurgical grade coal in particular are considered suitable raw materials 21.

If surplus thermal energy of the flue gas 12 continues to be available, it is possible in addition to utilize the thermal energy of the flue gas 12 downstream of the firing device 6 in an oil heat exchanger 23 for the purpose of heating a thermal oil 24.

In some cases it can be beneficial to adjust the temperature of the flue gas 12 heating the product gas 4. For this purpose cold-blast air 25 can be added to the flue gas 12 as shown in FIG. 2. In this case the admixing of the cold-blast air 25 takes place after the flue gas 12 has been used for steam generation, but—clearly—before the product gas 4 is heated.

It is possible to heat up the product gas 4 in the firing device 6 to a reaction temperature T (of typically in excess of 800° C.) that the product gas 4 must attain in order to be able to be used in the upstream plant 7. In many cases, however, it is advantageous to limit the heating of the product gas 4 to an intermediate temperature T′ that lies below the reaction temperature T. This applies even though, during the combustion of the heating gas 11, the thermal energy necessary for this (i.e. for heating to the reaction temperature T) is present. The intermediate temperature T′ can range from approx. 400° C. to approx. 600° C., for example. If the product gas 4 in the firing device 6 is heated only up to the intermediate temperature T′, the product gas 4 heated in the firing device 6 as shown in FIG. 2 is heated by a partial oxidation of the product gas 4 in an oxidation device 26 from the intermediate temperature T′ to the reaction temperature T. Normally, for this purpose, an oxidation gas 27, for example technically pure oxygen (oxygen content at least 90%) is supplied to the oxidation device 26 in addition to the product gas 4.

The heating gas 11 incinerated in the firing device 6 can in principle be selected arbitrarily. It is possible to supply the heating gas 11 to the metallurgical plant from outside. Alternatively, the heating gas 11 can be a gas generated within the metallurgical plant. For example, it is possible for some of the export gas 2 generated by the gas-generating plant 1 to be used as heating gas 11 according to FIG. 3. Alternatively or in addition it is possible to use the process gas 5 as heating gas 11. If necessary, a further combustible gas 28 can be added to the process gas 5. Alternatively the further combustible gas 28 can, if necessary, be incinerated in a separate burner of the firing device 6 together with the process gas 5.

If part of the export gas 2 or the process gas 5 is used as heating gas 11, a low-pressure gas accumulator 29 is preferably disposed in the supply line of the corresponding gas 2, 5 to the firing device 6. The low-pressure gas accumulator 29 serves to compensate for fluctuations in quantity and/or composition which occur during the generation of the export gas 2 and/or the process gas 5. A gas pressure p which is marginally greater than atmospheric pressure prevails in the low-pressure gas accumulator 29.

A gas 30 that is hot and/or combustible is produced in many cases during the operation of the upstream plant 7. This gas 30 is often referred to as top gas 30. If the top gas 30 is combustible, it is possible to admix the top gas 30—in its entirety or in part—to the export gas 2. Alternatively or in addition it is possible to utilize the top gas 30 as heating gas 11. Where appropriate it can be used in combination with the export gas 2 and/or the process gas 5. In particular the top gas 30 can in this case be identical to that combustible gas 28 which is mixed with the process gas 5 or incinerated together with the latter.

If the top gas 30 is hot, it is possible to utilize the thermal energy contained in the top gas 30 for preheating the product gas 4 before it is supplied to the firing device 6 and/or for steam generation (including superheating, where necessary). This also is indicated by dashed lines in FIG. 3.

The proposals have many advantages. In particular an efficient utilization of the thermal energy accumulating in the metallurgical plant and of the accumulating combustible gases is possible in a relatively simple manner.

The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004). 

1-16. (canceled)
 17. An operating method for a facility comprising a gas-generating plant, a steelmaking plant and an upstream plant disposed upstream of the steelmaking plant, the method comprising: generating an export gas in the gas-generating plant; removing carbon dioxide and/or water from the export gas, the carbon dioxide and/or water being removed in a separation device to produce a product gas; heating the product gas in a firing device to produce a heated product gas, the product gas being heated by combusting a heating gas to produce a flow of flue gas; supplying the heated product gas to the upstream plant; supplying the heating gas to the firing device in quantities significantly greater than are required for heating the product gas; using excess thermal energy produced during combustion of the heating gas in at least one of: generating steam in the firing device; preheating and/or drying raw materials supplied to the upstream plant and/or supplied to the gas-generating plant, the raw materials being preheated and/or dried using the gas flow of flue gas.
 18. The operating method as claimed in claim 17, wherein the excess thermal energy is used by first using the flow of flue gas for generating steam, and second using the flow of flue gas for heating the product gas.
 19. The operating method as claimed in claim 18, wherein cold-blast air is added to the flow of flue gas after using the flow of flue gas for generating steam and before using the flow of flue gas for heating the product gas, and the cold-blast air is used to adjust a temperature of the flue gas for heating the product gas.
 20. The operating method as claimed in claim 17, wherein combustion of the heating gas produces sufficient thermal energy to heat the product gas to a reaction temperature required to use the product gas in the upstream plant, heating of the product gas in the firing device is limited to an intermediate temperature below the reaction temperature, and the heated product gas is heated up from the intermediate temperature to the reaction temperature by a partial oxidation of the product gas.
 21. The operating method as claimed in claim 17, wherein combustion of the heating gas is performed with an oxidation gas, and the excess thermal energy is used to preheat the heating gas and/or the oxidation gas with the flue gas, downstream from the firing device.
 22. The operating method as claimed in claim 17, wherein the excess thermal energy is used for heating a thermal oil, the thermal oil being heated with the flue gas.
 23. The operating method as claimed in claim 17, wherein a process gas is produced when removing carbon dioxide and/or water from the export gas, the process gas being enriched with carbon dioxide and water, a portion of the export gas and/or the process gas is used as the heating gas.
 24. The operating method as claimed in claim 23, wherein the process gas is used as the heating gas, and the process gas is mixed with a more combustible gas before being fed to the firing device.
 25. The operating method as claimed in claim 23, wherein the portion of the export gas and/or the process gas used as the heating gas is buffered in a low-pressure gas accumulator disposed upstream of the firing device.
 26. The operating method as claimed in claim 17, wherein a top gas accumulates during operation of the upstream plant, the top gas is combustible, and the heating gas is formed by mixing respective portions of the top gas and the export gas.
 27. The operating method as claimed in claim 17, wherein a top gas accumulates during operation of the upstream plant, the top gas is a hot gas containing thermal energy, and the thermal energy contained in the top gas is used for steam generation and/or for preheating the product gas before the product gas is supplied to the firing device.
 28. The operating method as claimed in claim 17, wherein the upstream plant is embodied as a blast furnace, as a smelting reduction plant, as a smelter unit or as a direct reduction plant.
 29. The operating method as claimed in claim 17, wherein the gas-generating plant is embodied as a coal gasification plant or as a metal smelting plant.
 30. The operating method as claimed in claim 17, wherein the gas-generating plant is embodied as an iron melting plant or as a smelting reduction plant.
 31. A metallurgical plant comprising: a steelmaking plant; an upstream plant disposed upstream of the steelmaking plant; a gas-generating plant that generates an export gas; a separation device to at least partially remove carbon dioxide and/or water from the export gas to thereby generate a product gas; a firing device connected to the gas-separation device and the upstream plant, to heat the product gas, to produce a heated product gas and to supply the heated product gas to the upstream plant; a conduit to supply a heating gas to the firing device; and a conduit to supply and an oxidation gas to the firing device such that combustion of the heating gas and the oxidation gas produces a flow of flue gas, wherein the metallurgical plant further comprises at least one of: an evaporator disposed inside the firing device to generate steam from excess thermal energy produced while heating the product gas, and a raw materials processing device disposed downstream of the firing device in relation to the flow of the flue gas, to preheat and/or dry raw materials that are supplied to the upstream plant and/or to the gas-generating plant.
 32. The metallurgical plant as claimed in claim 31, further comprising a conduit to supply cold-blast air to the flow of flue gas.
 33. The metallurgical plant as claimed in claim 31, wherein the separation device produces a process gas enriched in carbon dioxide and water, the metallurgical plant further comprises a low-pressure gas accumulator to buffer the export gas or the process gas, and the low-pressure gas accumulator is disposed upstream of the firing device.
 34. The metallurgical plant as claimed in claim 31, wherein the upstream plant is a blast furnace, a smelting reduction plant, a smelter unit or a direct reduction plant.
 35. The metallurgical plant as claimed in claim 31, wherein the gas-generating plant is a coal gasification plant, a metal smelting plant or a smelting reduction plant.
 36. The metallurgical plant as claimed in claim 31, wherein the gas-generating plant is an iron melting plant. 